Intraocular lenses have gained wide acceptance in replacement of human crystalline lens after a variety of cataract removal procedures. The human crystalline lens is generally recognized to be a transparent structure having a thickness of about 5 millimeters and a diameter of about 9 millimeters. The lens is suspended behind the iris by zonula fibers which connect the lens to the ciliary body. A lens capsule surrounds the lens, the front portion of the capsule being commonly known as the anterior capsule and the back portion commonly known as the posterior capsule.
Numerous procedures for the removal of cataracts have been developed in which the lens is removed from the eye and replaced by an artificial lens implant. The extraction procedure may generally be categorized as intracapsular (in which the lens is removed together with the lens capsule) and extracapsular (in which the anterior capsule is removed with the lens, and the posterior capsule is left intact).
Since Ridley implanted the first artificial lens in about 1949, the problems associated with cataract extraction and lens implantation have received a great deal of attention from ophthalmic surgeons.
Various types of artificial lenses have been proposed, and appropriate surgical procedures have been developed which strive to reduce patient discomfort and to reduce post-operative complications. Reference is made in this connection to Pseudophakos by N. Jaffe, et al.; "History of Intraocular Implants" by D.P. Choyce (Annals of Ophthalomology, Oct. 1973); U.S. Pat. No. 4,251,887 issued to Anis on Feb. 24, 1981; U.S. Pat. No. 4,092,743 issued to Kelman on Nov. 8, 1977; "Comparison of Flexible Posterior Chamber Implants", presented at the American Intraocular Implant Society Symposium Apr. 23, 1982, by Charles Berkert, M.D.; and "the Simcoe Posterior Lens' (Cilco, Inc. 1980); pending U.S. Pat. Application Ser. No. 346,105 , now U.S. Pat. No. 4,573,998 for "Deformable Intraocular Lens Structures and Methods and Devices for Implantation" filed Feb. 15, 1982 by the inventor Thomas R. Mazzocco, and pending U.S. Pat. Application Ser. No. 400,665 for "Improved Fixation System for Intraocular Lens Structures", filed July 22, 1982, the latter applications being commonly assigned to the instant Assignee; which disclosures are hereby incorporated by this reference.
Conventional fixation systems for positioning and for fixating the artificial lens within the eye commonly involve the use of sutures for instance, for attachment of the lens to the iris, or involve the use of supporting haptic flanges to hold the lens in position without sutures.
Kelman, in U.S. Pat. No. 4,056,855, issued Nov. 8, 1977, describes an intraocular lens and a method of its implantation through an incision in the eye in which a lens member and a supporting wire initially in disassembled condition are adapted to be introduced independently through a small incision in the eye. The supporting wire of the Kelman lens has a base portion which is adapted to fit and be mounted behind the iris of the eye, and has a pair of resilient legs projecting from the pupil, forward of the iris which are adapted to receive a lens therebetween snapped into position by resiliently parting the legs while both components are located in the eye and thereby assembling and mounting the intraocular lens in position in the anterior portion of the eye for use.
Poler in U.S. Pat. No. 4,118,808, issued Oct. 10, 1978, discloses in one embodied form, a rim of an intraocular lens having a peripheral groove and a unitary mounting adapter which is formed to permanently assemble by resilient snap action into the groove. The adapter may be formed from a single piece "blank" and may be a circumferentially continuous structure. In unstressed condition, arcs are of curvature conforming to that of the groove and are preferably at a slight radially inwardly displaced position with respect to the circle of the groove. The arcs are outwardly spread against the compliant action of loops in order to permit placement and resilient snap retention of arcs in the groove. The assembly can then be sterilized and implanted in the eye.
While the prior art intraocular lens structures of Poler and Kelman referred to above, propose to hold an optic in place by a plurality of haptics which are interlocked and built up in the eye, these surgical procedures require extreme dexterity for accurate placement of the lens structure and for constructing the assembly and present a likelihood that less skilled surgeons may knick non-repairable ocular tissue such as the iris. Moreover, should the assembled optic and haptic split, its disassembly could cause laceration of the ocular tissue or cause the optic to be displaced from its intended position.
As with any surgery, an increased number of manipulations required to fixate the lens within the eye, increases the surgical trauma to the eye. Additionally, haptic components of conventional sutureless lenses can damage ocular tissue during intra-operative lens manipulation.
Flom (U.S. Pat. No. 3,991,426) and Hartstein (U.S. Pat. No. 4,262,370), teach sutureless iris engagement fixation systems, and Anis (U.S. Pat. No. 4,251,887) and Simcoe teach sutureless fixation systems utilizing broadly curved flexible supporting loop haptics. Unfortunately, the iris engagements systems require relatively significant trauma to the iris with attendant postoperative complications. The latter known systems, while achieving fixation with little or no trauma to the iris, can still become displaced through relatively small tears in the capsular bag when they are positioned there. These tears are not uncommon, and may occur during the removal of the cataract or during the insertion of the lens.
A wide variety of haptic fixating appendages for intraocular lens structures have been developed to foster improved fixation of the optical zone portion of the lens in specific implantation techniques and for particular sizing and implantation for the surgical procedure involved. For instance, intraocular lenses have been provided conventionally with fixating appendages having compressible internal support elements; integral and non-integral fixating appendages; angulated compressible fixating appendages with internal supporting elements; compressible peripheral support rings; to name but a few species.
Similarly, a wide variety of optical zone portions for intraocular lens structures have been developed to provide proper optical characteristics, that is, diopter power of the optic, appropriate optical finish, particular sizing and the like, to provide appropriate replacement or corrective features for the human crystalline lens of the patient.
Conventional haptic designs for intraocular lens structures generally require a second operation separate and apart from the molding or other fabrication of the optical zone portion of the lens. Typically, heat staking is required to fasten the haptic portion to the optical portion of the lens. In this respect, an optical zone portion may be molded, for instance, of a hard material such as PMMA, machined in a separate operation to remove flash and to drill sites for receiving the haptic portion. One preferred material for fabricating conventional haptics is polypropylene which is typically heat set to shape the polypropylene material at a temperature of about 225 degrees farenheit, but below the plastic transition temperature of the polypropylene material. After the conventional haptic portion is heat set, it is thereafter appended to the optical zone portion such as by tack welding in which the polypropylene is fixed to the drilled site in the optical zone portion.
One disadvantage of the foregoing conventional lens structures is that polypropylene haptics can be fabricated in a limited number of configurations owing to its relatively low temperature iependence and that generally, polypropylene is fabricated in round cross section by extrusion methods.
Additionally, owing to the relatively low temperature limitation of polypropylene haptics, the assembled conventional intraocular lens structure of these materials cannot be readily autoclaved in that typical autoclaved temperatures are within a range from about 240 degrees F. to about 250 degrees F., and may require autoclaving pressures up to about 15 atmospheres. As previously mentioned, such temperature ranges and pressures would destroy the heat set configurations of the polypropylene haptic portions.
Accordingly, those skilled in the art have recognized a significant need for an improved intraocular lens structure which affords the surgeon the choice of assembling a prescribed lens combination, that is, in terms of specific optical zone portion and specific configuration for haptic portion, which are custom tailored to a patient's individual needs. Further, those skilled in the art have recognized a significant need for an improved lens structure assembly which is autoclavable and which can be conveniently manufactured to produce a lens structure with integral haptic portion minimizing the risk of optic and haptic disassembly which could cause laceration of the ocular tissue or could cause the optic to be displaced from its intended position. The present invention fulfills these needs.